It's dangerous when the sidewalks are small and crumbling, and there are no bike lanes.
Not really. Just drive your bike like it's a car. Bike lanes and sidewalks are actually more dangerous than just riding your bike on the street. Most accidents are at intersections; drivers tend to only look for vehicles where they expect them, not on the side of the road (bike lane) or on the sidewalk.
I've found that even on (relatively) rural roads, riding on the shoulder signals to cars that they don't have to care about your presence, and they pass so close you wonder if they even saw you. Riding a bit into the road (say a bike width out) makes them explicitly pass you, with plenty of room (generally).
Do it! For any road where cars are going 35-40mph or less, I'd much rather take my chances with the road. If you're a decent biker you're going 15-20mph so you're from cars' perspective you're going < 20mph and very easy to see and avoid. For pedestrians, you're much bigger AND much faster, and there aren't well-defined rules, so you're very difficult to deal with.
On the sidewalk, you have a narrower, less predictable path, pedestrians, curb cuts, more frequent bumps, plus you're basically invisible to turning cars when going through an intersection. Visibility, road quality, and avoiding pedestrians are the biggest benefits to riding on the road.
For reference, I've bike commuted in Tampa, Provo (at the University), Stockholm, Chicago city and Chicago suburbs)
The thought is that they provide a false sense of security, and teach newer riders to be less aware of their surroundings, so when a new rider finds himself in traffic, he is less prepared.
Bike lanes are usually very close to parked cars. A door opens, and you are in the hospital.
Bike lanes are poorly striped at intersections. Sometimes they stick them to the right of all traffic lanes, so if a cyclist in the bike lane stays in it to go through the intersection, he is going to get right-hooked by turning cars. Sometimes the lanes are striped so that straight-through traffic is in the right place, but this encourages cyclists to do stupid things like making turns from the center lane.
Finally, the cars driving in the real traffic lanes push all the debris into the bike lane. That means you will be riding over wires, broken glass, etc., and that you will be very susceptible to flats.
Basically, once you are comfortable riding on the road, you will forget that bike lanes even exist. Riding a bike is statistically somewhat dangerous, but if you actively try to stay safe, you will.
(And oh yeah, please get some freakin' lights for your bike if you are going to ride at night.)
Not really. Just drive your bike like it's a car. Bike lanes and sidewalks are actually more dangerous than just riding your bike on the street. Most accidents are at intersections; drivers tend to only look for vehicles where they expect them, not on the side of the road (bike lane) or on the sidewalk.